It is known to combine a blender with an ice shaver in a single appliance, as disclosed for example in U.S. Pat. Nos. 6,793,167 and 8,282,268. Such appliances are used in restaurants and bars to produce frozen drinks. The restaurants and bars are often in warm and humid locations where frozen drinks are desirable.
FIGS. 1 and 2 illustrate a combined ice shaver and blender of the prior art. The blender functionality may be provided by a blender cup having an impeller at the bottom of the cup. The impeller may be coupled to a ferrous drive plate rotatably mounted in a base of the blender cup such that the impeller rotates with the drive plate. The blender cup is removably received on top of a magnetic drive of the appliance configured to magnetically drive rotation of the drive plate in the blender cup, thereby causing rotation of the impeller. The magnetic drive may include a brushless d.c. motor having stator windings and a rotor assembly, wherein the rotor assembly includes a ring-shaped drive magnet carried in a hub and configured to magnetically drive rotation of the drive plate in the base of the blender cup. In some embodiments, the drive ring magnet is about five inches in diameter and weighs approximately three pounds. With typical operating speeds varying from 4,000 to 10,000 rpm, the rotating drive ring magnet can exert significant forces on the mounting structures, particularly rapidly varying forces that produce noise and vibrations. Heat and pressure buildup within a housing of the drive motor are concerns during motor operation. The stator windings and sensing electronics for providing motor control feedback must be protected from exposure to liquid, so an open-vented housing is not an available solution for relieving heat and pressure buildup.
What is needed is an improved magnetic drive design capable of dissipating heat and pressure associated with operation of the drive motor.